In known manner, a gas turbine rotor blade comprises an airfoil formed with a suction or convex outer surface and with a pressure or concave inner surface, which surfaces are interconnected at their upstream ends by a leading edge and at their downstream ends by a trailing edge, where “upstream” and “downstream” are relative to the gas flow direction. The airfoil is connected by a platform to a blade root of the dovetail, Christmas tree, or similar type for insertion in a corresponding cavity of a rotor disk of the gas turbine. At least one reinforcing web, referred to as a “stiffener”, is formed at the downstream end of the platform on its side opposite from the airfoil and it extends transversely, being connected to the blade root.
The blade also includes cooling means whereby a fluid such as air flows through ducts that are formed inside the airfoil and the blade root by casting. The cooling air escapes in particular via exhaust slots opening out downstream along the trailing edge and oriented substantially perpendicularly to the longitudinal axis of the blade and parallel to the platform.
The zone where the trailing edge connects with the platform lies between a cooling air exhaust slot and the stiffener, and it is the radially inner portion of the stiffener that is cooled by contact with the cooling air. This connection zone is thus remote from cooling air and it is in contact with the hot gas flowing through the turbine, so it is subjected to intense thermal stresses, leading to the formation of cracks that can destroy the blade and also the turbine.
Proposals have already been made to cool this connection zone by a flow of air leaving through orifices formed in the platform and opening out into the suction surface, but that configuration is not mechanically satisfactory.